I. Field of the Invention
The invention relates to a fiberizing installation delivering fibers, especially glass fibers, and more particularly to the mechanical reinforcement of one of the components of the fiberizing installation.
II. Description of Related Art
Conventionally, a fiberizing installation comprises a glass flow block, which receives molten glass coming from a feeder connected to the furnace in which the glass is melted, a bushing block and a bushing. The bushing is provided at the bottom with a plate provided with a multitude of holes from which the molten glass flows, to be drawn into a multiplicity of filaments.
These filaments, the diameter of which may vary from 5 to 33 μm, are collected into at least one sheet that converges on an assembling device in order to form at least one strand and, for example, to be wound up. Depending on its use, the strand may also be chopped (to form chopped strands) or thrown onto a belt (to form continuous strand mats).
The products obtained are used mainly in various reinforcing applications.
The bushing is manufactured from an alloy of platinum and rhodium, which materials are electrically conducting and resistant over time to very high temperatures. This bushing is heated by the Joule effect (resistance heating) so as to maintain, at a certain temperature, around 1100 to 1400° C., the glass that it contains so that it remains in the molten state so as to be drawn from the holes in the bottom of the bushing. The bushing is heated using an electrical transformer by the connection of two terminals, each located on each of the opposed ends of the bushing, to electrical connection components external to the bushing.
The terminals of the bushing are attached by welding them to the side walls of the bushing. They project so as to be connected to the external connection components.
Placed inside the bushing, in a plane substantially parallel to the bottom of the bushing and on the bushing block side, is a screen intended to thermally condition the glass and to absorb some of the hydrostatic pressure exerted by the molten glass.
The molten glass exerts high stresses, of around 6000 Pa, on the sides, the screen and the bottom of the bushing. Over the course of time, these stresses, combined with the heat, tend to distort the bottom, the screen and the sides of the bushing. Furthermore, the external electrical connection components connected to the terminals of the bushing are suspended therefrom, exerting an additional mechanical tensile force on the bushing, which also causes the bushing to deform over time.
Over the course of time, the hot creep of the constituent materials of the bushing, combined with the hydrostatic pressure of the molten glass, tends to deform the bottom, the screen and the sides, consequently causing strand quality and titer uniformity problems and yield problems.
The tensile forces (weight) of the suspended components and the linear expansion of the walls of the bushing also induce high mechanical stresses.
So as partly to prevent deformation of the bushing, it is known to add, in the upper part of the bottom of the bushing and between its sides, a plurality of mutually parallel reinforcement components lying in planes transverse to the plane of the bottom of the bushing and transversely to the longest sides of the bushing. In the rest of the description, the terms upper and lower are defined relative to the flow direction of the glass through the bushing, the glass being drawn from the upper part toward the lower part.
U.S. Pat. No. 3,920,430 discloses such a reinforcement component or device which helps to improve its resistance to bending, while not increasing the weight of platinum or platinum alloy needed for its construction, by additionally providing a ceramic rod placed inside the reinforcement component.
In that document, the reinforcement component consisting of a longitudinal bar is hollow and houses a ceramic rod that extends beyond each of the ends of the reinforcement bar and is anchored into the concrete for packing the bushing. That document insists on the fact that the rod is placed in the upper part of the reinforcement bar, bearing on the upper internal wall of the bar and leaving an empty space in the lower part of the bar.
However, this reinforcement bar, owing in particular to the internal empty space in the lower part, is not sufficiently resistant to bending. Furthermore, owing to the platinum creep temperature, the bar deforms, its lower part slumps and the thrust forces exerted by the glass on the bottom of the bushing end up by deforming it.